1. Field of the Invention
The invention relates to an optical device and a display apparatus having this optical device, and more particularly to a wavelength conversion device and a projector having this wavelength conversion device.
2. Description of Related Art
Recently, projection apparatuses which adopted solid state light sources such as light-emitting diode (LED) and laser diode have gradually became the mainstream in the market. Since a laser diode has a light emitting efficiency higher than about 20%, pure light sources of a projector which are generated by exciting phosphor powder with laser diodes are gradually being developed, in order to break through the limits of LED light sources. In addition, a laser projection apparatus can excite phosphor powder with laser, and it can also directly use the laser as a light source of the projector, and the laser projection apparatus has advantage of adjusting the number of light sources according to demand of brightness, in order to achieve the demand of the projector with different brightness. Therefore, using a laser as a light source of projector architecture has a tremendous potential to replace methods of using conventional ultra high pressure (UHP) lamps and become a new mainstream of light sources of projectors.
In existing laser projectors, a phosphor wheel is formed by filling phosphor powder on a metal substrate with high reflectance, and light with different colors (e.g. green light and yellow light) is generated by exciting the phosphor powder on the metal substrate with a laser emitted by a laser light source, and the laser (e.g. blue light) can directly go through the phosphor wheel by going through a slot on the metal substrate, in order to generate light with multiple colors. In the aforementioned design, the slot will make wind-cut noise during the rotation of the metal substrate. In addition, during the rotation, in order to prevent the wobble due to the asymmetric structure created by the slot of the metal substrate, another slot is being added on metal substrates of some phosphor wheels to acquire the symmetric structure of the metal substrate. However, adding another slot is making the problem of wind-cut noise become even worse, and reducing heat dissipation area of the metal substrate resulting in the reduction of heat dissipation efficiency of the phosphor wheels.
According to the invention disclose by the U.S. Pat. No. 8,157,398, a light emission wheel is applied to a projector, and the light emission wheel includes an opaque substrate and a transparent diffusion substrate attached to the opaque substrate. A blue excitation light emitted by a light emitter can excite phosphor powder on the opaque substrate or directly pass through the transparent diffusion substrate. According to the invention disclosed by the Taiwan patent application no. 200837483, a color wheel component is applied to a projector. The color wheel component includes a gasket and a color filter, and the color filter is embedded in the slot of the gasket.